Dental chair and the like



Feb. 21, 1956 J. wURM ETAL DENTAL CHAIR AND THE LIKE 4 Sheets-Sheet 1 Filed Aug. 24, 1951 INVEN Joszpjh WZLIPIVZZ .sep aye arm TORS Jig e ATTOR Feb. 21. 1956 J. WURM ET AL DENTAL CHAIR AND THE LIKE 4 Sheets-Sheet 2 Filed Aug. 24, 1951 Warm WE o eV m mWm/ m 7 hw 0 M w 6 ..e A 6 mh w mm Wm an, |||....A. 8 I w/ n/ I 7 8 J?" 7 4 n 8 8 7 L 0 fi mw 1 2% W o W 5a 7 4 0O 0 w m a J. WURM ETAL 2,735,477 DENTAL CHAIR AND THE LIKE Feb. 21, 1956 4 Sheets-Sheet 3 Filed Aug. 24, 1951 lNylE TORS Jozep arm re? yeolye WLLINL m W MM A j TT EYS DENTAL CHAIR AND THE LIKE =41 Sheets-Sheet 4 Filed Aug. 24, 1951 arm 6 Wurmx W r R E 70 Vhe 1T M 0 P United States Patent 2,735,477 DENTAL crrAm AND THE Luna Joseph Wurm and Joseph George Worm, Maspeth, N. Y.

Application August 24, 1951, Serial No. 243,438

4 Claims. (Cl. 155-25) This invention relates to dental chairs or the like having extensible mechanism for raising and lowering the chair, and more in particular to dental chairs which are raised by oil under pressure pumped by a motor driven rotary pump.

The illustrative embodiment of the invention involves hydraulically (i. e., oil) operated, telescoping, extensible members which are more or less of a conventional type for raising and lowering such chairs, but there are improvements which render the chair superior to prior chairs. The hydraulic system of the invention is fully automatic, and involves important improvement features. A principal feature of the invention is a control valve of novel construction which is arranged to be operative to interrupt the delivery of the oil under pressure to the lifting mechanism, and which simultaneously releases the oil pressure from the pump so that it is returned to the oil supply sump.

This valve operates to control the hydraulic system in such a way that the chair can be raised very smoothly and uniformly, and with accurate control and ease, and can be lowered and stopped gently and quickly at any desired point.

This valve is of the cylinder and axial plunger type, and the plunger has a central bore through which the oil flows to two alternate discharge channels. One channel is to the oil sump through a relief port which is at the end of the cylinder, and the other channel is through an oil discharge port through which the oil under pressure is delivered to the chair elevating unit. By a short sliding movement of the plunger from its normal position, the oil discharge port is closed and the relief port is opened so that continued operation of the pump has no effect.

It is an object of the present invention to provide an improved and automatically operating and adjustable hydraulic chairs, particularly by providing an improved control for the hydraulic fluid system. Another object is to improve the automatic control of the extensible means in a hydraulically operated chair by providing an automatic valve controlling the supply of hydraulic pressure to the extensible means and simultaneously operable to vent the hydraulic system to a sump.

It is a further object to provide for the conversion of manually operable dental chairs or the like to electric motor operation, and to provide absolute safety of operation. It is a still further object to provide for the above with structure which is thoroughly practical in every respect and which is adaptable to meet the various conditions encountered in use.

Further objects and numerous of the advantages of the invention will become apparent from the following detailed description and annexed drawings wherein:

Figure l is a view of a dental chair having my invention embodied therein;

Figure 2 is a view on the line 22 of Figure 1;

Figure 3 is a partially sectional view of a portion of the chair;

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Figure 4 is a detail view partly in section of the main hydraulic control valve.

Figure 5 is a detail sectional view of a part of the structure of Figure 4; and

Figure 6 is a somewhat schematic view of the hydraulic system of the chair of Figure 1.

Referring to Figure l of the drawings, there is shown a dental chair comprising a seat portion 10, having a seat 12 and side arms 14 carried by a frame 15, and an apron 16 forming a foot support. The chair has a back 18 supported from a bracket 20 which is adjustably supported from a back support member 26 having a slide which is engaged by the member 20, the member 20 being latched in the desired position by the latch member 28. Back support member 26 is attached to the chair frame 15 by bolts 32 and 34.

The base of the chair is formed by a hollow stationary pedestal 36 having a circular platform 37 resting upon the floor and a cylindrical sump casing 39 fixed thereto. Rotatably mounted in casing 39 is a pedestal or cylinder 40 which acts as a turnable pedestal, and is of reduced diameter and provides a turnable mounting frame and casing for the extensible elevating chair mechanism. The entire chair is supported by the turnable pedestal or cylinder 48 which is supported by an integral flange 42 having an annular supporting surface overlying and resting upon the top edge of the stationary casing 39. This mechanism includes a cylinder 38 which telescopes within the pedestal and which has at its lower end a pair of guide brackets or ears 44 (only one of which is shown) which engage and slide along a pair of guide posts 46 fixed to the pedestal, thus to guide the vertical movement of cylinder 38. Telescoped within cylinder 38 is an inner cylinder 48 which is slidably mounted and guided by a pair of brackets or cars 50 which engage and slide along a pair of vertical posts 56 (only one bracket and post is shown) carried by cylinder 38. Cylinder 38 (see Figure 2) has side ribs 62 which mate with grooves in a cover ring 82 clamped to the top of the cylinder 40 by cap screws 84 so that these ribs assist in guiding the movement of the cylinder. The top of cylinder 38 carries a somewhat similar cover ring 63 which has grooves mating with side ribs 64 on cylinder 48 so as to assist in guiding the movement of the inner cylinder.

The hydraulic system for elevating the chair includes a hydraulic pump 70 (see also Figure 6) driven by an electric motor 86. Pump 78 is of the rotary type with an inlet or suction conduit 72 and a discharge or outlet conduit 74. The pump is mounted on the motor casing, and the motor and pump are mounted as a unit on cylinder 40 by a clamping bracket 76 which has a split ring portion 71 clamped around the motor by a bolt 73 extending through integral ears. Bracket 76 also has a vertical portion which rests against the side of cylinder 40, and a horizontal portion 77 which is clamped against the top of cover ring 82 by one of the cap screws 84 (see Figure 3). Each of cap screws 84 extends through an arcuate portion 81 of the cover ring 82 which extends into the top of cylinder 40, and the cap screws are threaded into bushings 83 which have been turned into threaded openings in the cylinder. Conduits 72 and 74 (Figure 6) extend into the cylinder 40 through an extension bracket with the inlet conduit having its end connected to draw oil from the oil sump formed by the bottom of the stationary pedestal. Discharge conduit 74 extends to a control valve 102 to be described more in detail below.

Centrally positioned in cylinder 40, and projecting into cylinders 38 and 48 when these cylinders are nested, is a piston and cylinder elevating unit 65. Unit 65 is formed by a stationary piston 66 having a piston rod 61 which is centrally mounted at its lower end at the bottom cylinder 40, and which projects upwardly with its piston portion carrying a vertically movable cylinder 67 which comprises the other element of the unit 65. Cylinder 67 carries at its lower end a pair of radial arms or brackets 69 which extend beneath cylinder 48 and are attached by screws to the bottom of the cylinder 38. The rod 61 of piston 66 has a central bore 92 through which the oil under pressure is pumped into cylinder 67 so that the cylinder is caused to slide upwardly with respect to the piston; this movement is transmitted to cylinder 38, which is thereby lifted. Cylinders 38 and 48 are mechanically connected by a chain and sprocket roller assembly (of known type) whereby any given vertical movement of cylinder 33 causes cylinder 48 to move twice as much and in the same direction. This chain and sprocket assembly need not be described in detail here.

Referring to Figure 4, the lower end of piston rod 61 is connected by a couping 96 to a transverse beam or support member 98 rigidly clamped to the bottom of cylinder 40. Beam 98 has a fluid channel 100 therein 1 which connects with bore 92 in rod 61. The hydraulic fluid control valve 102 is rigidly mounted upon beam 98 and has a housing 104 at the base and an upstanding cylindrical sleeve 106. Housing 104 has an open bottom covered by a disc screen 101 and the housing is positioned in the oil sump immersed in the body of oil. The oil inlet conduit 72 from the oil pump 79 (Figure 6) is connected to a fixture 103 (Figure 4) which terminates at an oil inlet nipple 165. Nipple 165 is positioned with its open mouth directly above screen 1121 so that the oil from the sump is drawn through the screen into the nipple and it passes to the pump through the conduit '72. Within sleeve 106 is a valve casing or cylinder 108 within which is a sliding valve plunger or piston 110 forming the control valve. The upper end of cylinder 108 is internally screw threaded to receive a fitting 112 to which the pump outlet conduit 74 for oil under pressure is connected by a coupling 116. A coil spring 118 is positioned in cylinder 108 between fitting 112 and plunger 110 downwardly. The lower end of the plunger forms a valve portion 119 which mates with a valve seat 120 of a discharge port 121 formed in the lower end of cylinder 108; and the plunger 11d has a downwardly extending operating stem 122 extending through the valve port as will be referred to again presently.

Plunger 110 has a central bore 124 extending from its upper end and in communication with the oil under pressure entering through conduit 74. The plunger also has centrally positioned on its outer surface an annular groove 126 which forms an annular chamber at the inner wall of cylinder 108; and, four radial ports 128 extend from this chamber to the central bore 124 and provide communication from the central bore and to this annular chamber. Adjacent annular chamber 125 there are a large number of transverse ports 132 in the side wall of cylinder 108 which communicate with a relatively extensive annular chamber 134 formed by the inner surface of sleeve 106 and a groove in the outer surface of cylinder 108. The lower end of plunger 110 is of reduced diameter and forms with cylinder 108 an annular chamber 136, and four radial ports 14% extend inwardly from this chamber to bore 124 providing communication between the bore and the chamber.

When plunger 110 is lifted so as to unseat valve portion 119, the oil under pressure may flow from the central bore 124 through ports into annular chamber 136 and then through the port 121 into housing 104; the oil is thus delivered to the sump in the lower part of the pedestal. When plunger 110 is positioned as shown, the oil in central bore 124 passes through the radial ports 128 into annular chamber 125 and thence through ports 132 into annular chamber 134, and it is directed to the extensible mechanism of the chair in a manner to be described. However, when the plunger is lifted to open the valve port 121 as described, the

4 ports 132 are closed by the portion of plunger 110 beneath groove 126, and oil can not pass to chamber 134. The hydraulic valve is lifted by a lever arm 144 having a hook 146 at its lefthand end which rides on a transverse pin 148 mounted at its ends in housing 168 (see also Figure 5). Lever arm 144 engages the valve stem 122 and has at the right (Figure 4) a vertical operating rod 150 which extends through an operating bracket 153 on cylinder 38 which will be referred to below.

Referring again to Figure 5, the annular chamber 134 communicates with a transverse channel 152 in housing 1198 leading to a check valve 154 formed by a valve member 155 urged upwardly against a seat by a coil spring 156. The coil spring 156 is in a cylindrical bore 158 in housing 108 and is retained by a screw plug 160 threaded into the bore. The check valve 154 prevents the flow of oil upwardly, but when oil under pressure is delivered through valve 102 to channel 152, the valve member 155 is unseated by the oil pressure and the oil flows downwardly through the valve. Then, as indicated above, beam 98 has a bore 100 which is transverse to bore 152 and with valve 154 open, connects bore 152 with the bore 92 which extends through tthe piston rod 61 and piston 66 to the interior of cylinder 67. Thus, when the plunger 110 of valve 102 is positioned as shown, the oil under pressure from the pump passes through passageway 152 and unseats the check valve and flows through the bores 100 and 92 to the cylinder 67 and the chair is thereby elevated. However, when the valve plunger 11%) of valve 102 is lifted, the ports 132 are covered by the valve plunger, and the discharge port 121 is opened so that the oil from the pump flows from the valve 102 back to the oil sump. Therefore, when the plunger is seated as shown, the operation of pump 70 causes the oil to pass to the cylinder and elevate the chair;

but, when the plunger is lifted, the oil passes from the pump through conduit 74 and valve 102 back to the sump.

Referring again to Figure 6, the electric circuit of the pump motor 86 includes a mercury switch 166 and also a control switch 164 which the dentist closes by his hand or his foot to operate the motor and elevate the chair. The mercury switch is a safety device and it is normally closed, but is opend so as to stop the motor if the chair reaches its fully elevated position. This switch is mounted (see also Figure 3) upon the motor clamping bracket 76 by a fixed disc 174 which has a metal mounting bushing 173 threaded into the vertical portion of the bracket, and the switch is carried by a bracket 169 which has a pivot pin 170 journalled in this bushing. The switch is swingable to the open-switch position of Figure 6, but is biased to the closed-switch position of Figure 3 by a coil spring 172 having its arms anchored respectively to disc 1'74 and to an angle arm 168 fixed to bracket 169. Arm 168 carries a rigid operating pin 176 which is engaged by the toe 177 of an operating rod 178. Rod 178 is carried at its upper end by a curved saddle plate 180 to which it is adjustably fixed by a. set screw 181. Saddle plate 180 has a central stem 182 which extends into a journal sleeve 183 fixed in the cover ring 82. The saddle plate also has an integral sleeve 135 which also extends downwardly through an opening in cover ring 32 and the lower end of sleeve 185 is externally threaded and has a nut 187 thereon. Surrounding sleeve 185 and compressed between the bottom of cover ring 32 and nut 137 is a spring 190 which normally biases the saddle plate 180 toward the position shown wherein it rests upon the top of the cover ring. Slidably mounted in sleeve 185 is a rod 184 which is threaded at its ends with a nut 189 on its lower end and a pair of nuts 191 on its upper end which clamp the top of the rod to an ear or bracket 188 which is clamped to the top of cylinder 33 (see Figures 1 and 6).

Thus, rod 184 is moved up and down with cylinder 38 and during such movements slides through sleeve 185. However, when cylinder 38 approaches the fully elevated position, rod 184 slides upwardly sufiiciently for nut 139 to engage the bottom of sleeve 185. Thereafter, further movement lifts the sleeve against the action of gravity and spring 190 and this lifts the s 1ddle plate 180 and also the operating rod 178 pulls up On pin 176 so as to swing the mercury switch 166 from the closed-switch position of Figure 3 to the open-switch position of Figure 6. As indicated above, this stops motor 86 and therefore stops the pumping of oil to the elevating unit 65. Thereafter, when the chair moves downwardly the sleeve 185 and the saddle plate return to the position of Figure 3 and the mercury switch is reclosed. It should be observed that the spring 190 not only facilitates the rapid reclosing of switch 166, but it also insures that the saddle plate and the parts associated therewith will move up and down smoothly without any binding action.

In addition to the safety function effected by opening the mercury switch 166, the elevating mechanism is protected by the mechanical means for operating valve 102 whenever the elevating mechanism reaches its fully elevated position. Referring again to Figure 4, the valve plunger 110 is lifted so as to open the oil discharge port 121 by pulling up on the lever arm 144 through the operating rod 150. As indicated above, rod 150 extends upwardly through a bracket 153 which is carried by cylinder 38. Thus, as the cylinder moves upwardly to the elevated position, it pulls rod 150 (see Figure 6) and acts through arm 144 (Figure 4) to open the relief port 121. Therefore any oil which is delivered by the pump through conduit 114 is returned through the valve to the oil sump, and even if motor 86 continues to operate the oil is no longer delivered to the elevating cylinder 67. In this way a mechanical safety feature is provided, along with the electrical safety feature formed by switch 166.

Referring now again to Figure 6, the chair releasing pedal 194 which is normally spring-urged to the elevated position shown is pushed down by the dentists foot to permit the chair to move downwardly from an elevated position. The depressing of pedal 194 opens a discharge valve (not shown) to discharge oil from cylinder 67 to the oil sump.

In the illustrative embodiment, the invention is incorporated in a dental chair so as to give very important advantages not present with the prior structures known to us. Under some circumstances a substantially identical construction can be used for other types of equipment, such as barber chairs and medical and surgical chairs, and other supporting devices such as tables. Furthermore, with certain applications of the invention, the elevating and control mechanism may be changed while retaining the advantages of many of the very important aspects of the invention. Thus, the dentist steps on the switch 164 to elevate the chair to any desired amount, and he then pushes on the pedal 194 to permit the chair to move down again.

As many possible embodiments may be made of the mechanical features of the above invention, without departing from the scope of tit) invention, it is to be understood that all matter hereinabove set forth, or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

We claim:

1. In an adjustable chair, in combination, hydraulically operated extensible means for raising and lowering the chair, a pump for hydraulic fluid, an electric motor for driving said pump, means forming a hydraulic fluid sump, means forming a hydraulic circuit including said extensible means and a by-pass valve to divert the hydraulic fluid from said pump directly to said sump, means responsive to a predetermined upward movement of the chair controlling the by-pass valve, electric circuit means controlling said motor and including a switch, and switch operating means comprising a vertical-sliding bracket and a vertical rod associated therewith and positioned to be raised by the moving of the chair to its fully opened position whereby the switch is responsive to movement of the chair to stop the motor.

2. Apparatus as described in claim 1 wherein said sliding bracket means comprises a saddle plate having a center guide pin resting in an opening, and a downwardly extending operating means which operates said switch.

3. Apparatus as described in claim 2 wherein said pump and said motor are mounted as a unitary structure upon the pedestal of the chair, and wherein said electric circuit means includes a switch which is closed to operate said motor.

4. Apparatus as described in claim 3 which includes, a fixed housing providing a mounting for said chair, and a pair of conduits including an inlet conduit adapted to withdraw fluid from said housing and pass it to said pump and a discharge conduit adapted to receive fluid from said pump and pass it to said valve.

References Cited in the file of this patent UNITED STATES PATENTS 1,101,920 Garbutt June 30, 1914 1,219,334 Lower Mar. 13, 1917 1,436,018 Dieter Nov. 21, 1922 1,656,760 Schramm Jan. 17, 1928 1,770,197 Carter July 8, 1930 1,850,966 Harris Mar. 22, 1932 1,920,047 Zoerb July 25, 1933 2,215,666 Meitzler Sept. 24, 1940 FOREIGN PATENTS 489,834 France Nov. 5, 1918 

